Kent,
A properly setup vacuum secondary kicks in "on demand" when there is a need
for more flow. With just the primaries you get better response due to higher
mixture velocity as well as better efficiency. I will agree that it is not
necessarily easy to get the Q-Jet to behave the way you want it to, but it
really can be a good carb if you take the time to learn it. Nonetheless, The
Rochester QuadraJet is not really a vacuum-activated secondary. If you look
at the throttle action, you will see that the secondaries open mechanically
regardless of the presence of vacuum. Air-flow affects the mixture, but not
the opening. The worst of both worlds in a way. I was refering to the Holley
vacuum-activated secondaries on which manifold vacuum (or lack thereof)
actually controls the throttle of the secondaries. Much better carb
design-wise, but not as well built as the Q-Jet.
David Lieb
1972 Blue
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